The first thing that comes to mind is childhood friends. Why do majority no longer keep in touch with them? The answer may lie in the building of the friendship itself. How do two kids become friend? When they have something in common. As we age, our lifestyle, preference, and interest changed. Also, we meet new people.
"Shut up! If you cut him out, we will just be line segment of friends!"
"No, I will cut you off and just be a dot!"